Extruding metal tubes prom wire



July 26, 1966 Filed Au 1, 1962 5 Sheets-Sheet 1 Qom chm

INVENTOR.

HERBERT L. MZCLELLAN w. 7%; WWW ATroRrys July 26, 1966 H. L. MCCLELLAN 3,262,303

EXTRUDING METAL TUBES FROM WIRE Filed Aug. 1, 1962 5 Sheets-Sheet 2 INVENTOR.

HERBERT L. M CLELLAN BY R/(HE); NA/lVA/Y/FA/PR/IVG 704 ATTORN S July 26, 1966 H. L. McCLELLAN EXTRUDING METAL TUBES FROM WIRE 5 Sheets-Sheet 3 Filed Aug. 1, 1962 m L! w. r gm Z m M x N u p w nw mw w E m 5/ m I 90$ 8 mm 2 A8 M Mi 1 OW. L N. U ||1 2., E. 1 .w T m I" mt i|l|| m w M w.l!| mm 5 .P x H W W mm mm w N? N 4 mv Lrlr/ yn m I S ll R\1BA fllllm A III mmxwm 1F HH||| f g x eff" ATTO EYS July 26, 1966 H. L. McCLELLAN EXTRUDING METAL TUBES FROM WIRE N7 fQ QO.

Filed Aug. 1, 1962 ATToRfi M 4 mm; b. mix/ m m mu. h VLF. M m a m2 1 .C/ m mm. s m- T u m B mmww a w mm mdE July 26, 1966 H. L. McCLELLAN 3,262,303

EXTRUDING METAL TUBES FROM WIRE Filed Aug. 1, 1962 I 3 INVENTOR.

H ERBERT L. MCC LE LLAN ATTORN YS United States Patent (This) Filed Aug. 1, 1962, Ser. No. 213,999 4 Claims. (Cl. 72-368) This invention relates generally to the extrusion of hollow articles and more particularly to a novel and improved method and apparatus for forming extruded hollow articles such as collapsible tubes, aerosol cans and the like from blanks cut from cylindrical wire or rod stock.

With a method and apparatus incorporating this invention, the working of the material forming the article is substantially uniform throughout and is symmetrical with respect to the extrusion operation. The initial blank is cut from wire or rod stock wherein the initial length of the blank is at least substantially equal to the initial diameter thereof. The initial blank is then symmetrically upset to form an intermediate cylindrical blank having a diameter substantially greater than its length. The intermediate blank is extruded symmetrically with respect to the blank axis. This symmetrical working produces substantial advantages even when the metal being formed has little or no cold working properties. Even such noncold working metals have flow lines formed by the working thereof. These flow lines may produce non-uniformity in the finished article if the flow lines of the blanks are not similarly oriented from one piece to the next. Since all working with this invention is symmetrical about the original axis of the material, similar flow line orientation is always provided and improved article uniformity is achieved.

When forming articles from metals which work harden such as light metal alloys, brass and steel, it is desirable to provide uniform working of the material since the grain size of such material is reduced by cold working and improved strength of the finished article results. However, if the working is not substantially uniform, there is present in the material excessive grain contrast produced by uneven working. Such excessive grain contrast may produce grain growth of the larger grains at the expense of the smaller grains during aging and produces planes of weakness which often result in cracks. Such grain growth during aging does not occur if the grain contrast is not excessive and the strength of the article remains high, since the grain size remains small. To insure the absence of excessive grain contrast, the working is maintained substantially uniform.

Here again, with work hardening metals, the existing flow lines of the material effects the subsequent flow of cold working and also effect the flow lines in the grain structure present after such cold working. The working is symmetrical about the central axis so that the symmetrical flow lines are formed in the intermediate blank.

This insures that the extrusion will be uniform and the grain of the finished article is uniform.

A completely automatic machine is provided which performs all of the manufacturing steps, from the shearing of the initial blank from the wire stock to the extrusion of the finished article. The steps of the manufacture are performed with uniform short periods of time between each operation and any aging which occurs is therefore uni-form. As a result, uniformity of the finished article is achieved. The automatic processing also eliminates the need of blank storage thus reducing inventory costs and also prevents the occurrence of bent or mixed blanks which interfere with proper performance of the various manufacturing operations.

It is an important object of this invention to provide a novel and improved method and apparatus for forming extruded hollow articles from cylindrical blanks sheared from rod or wire stocks.

It is another important object of this invention to provide an apparatus for forming hollow extruded articles from rod or wire stock without intermediate handling or storage.

It is another important object of this invention to provide a novel and improved method of forming extruded hollow articles having a high degree of structural uni formity.

It is another object of this invention to provide a novel and improved method and apparatus for forming blanks for later extrusion wherein the material of the blank has substantially uniform physical properties and the grain structure thereof is symmetrical about the central axis of the blank.

It is still another object of this invention to form hollow articles having substantially uniform grain size symmetrically oriented about a central axis thus eliminating weaknesses from occurring during aging.

Further objects and advantages will appear from the following description and drawings wherein:

FIGURE 1 is a plan view of a machine incorporating this invention with parts removed to simplify the understanding thereof;

FIGURE 2 is a vertical section of the machine illustrating the arrangement of the die breast and transfer mechanism;

FIGURE 3 is a longitudinal section of the first die stat-ion illustrating the dies and tools for performing the initial upset of the blank;

FIGURE 4 is a longitudinal section of the dies and tools of the second station wherein the blank is socketed;

FIGURE 5 is a longitudinal section of the third station dies and tools wherein a slug is punched out of the blank forming a central bore therethrough;

FIGURE 6 is a longitudinal section of the dies and tools of the extrusion station wherein the completed article is extruded;

FIGURE 7 and FIGURE 8 are fragmentary views illustrating progressive positions in the extrusion operation;

FIGURE 9 is a longitudinal section of the initial blank cut from cylindrical stock illustrating the grain pattern;

FIGURE 10 is side and end views of the blank formed at the first die station illustrating the grain pattern;

FIGURE 11 is side and end views of the socketed blank completed at the second die station with grain pattern illustrated;

FIGURE 12 is side and end views of the blank with the slugs cut therefrom completed in the third die station; and

FIGURE 13 is a side elevation partially in section of the extruded finished article.

Referring to FIGURE 1 the numeral 10 designates a bed frame of any suitable design. A main crank shaft 11 is journaled in the opposite sides of the bed frame and is provided with a crank 12 and a connecting rod 13 journaled thereon. A countershaft 14 is geared to the crank shaft 12 for rotation at the same speed as the crankshaft. The bed frame 10 is provided at its forward end with a die breast 16 and within a slideway formed in the frame, a slide 17 is mounted to reciprocate toward and away from the die breast 16. The connecting rod '13 is journaled on the slide 17 to produce a complete cycle of reciprocation thereof during each revolution of the crankshaft 11.

Wire or rod stock 18 is fed through the bed frame 10 by any conventional type of feed rollers or the like and is sheared at a shearing station 19 to form the initial blank 21 illustrated in FIGURE 9 which is transferred to the first die. The initial blank 21 has a length at least as great as its diameter and is cylindrical in shape.

Referring to FIGURE 2, the stock is engaged by a shear including a vertically reciprocable knife 22 which shears off the blank 21 and carries it upward into horizontal alignment with the blank working stations wherein it is gripped by a first pair of transfer fingers or scissors 23. A knockout (not shown) is used to push the sheared blanks from the knife 22. A detailed description of this shearing mechanism is contained within the United States patent to Friedman No. 2,721,343, dated October 25, 1955.

The transfer mechanism is arranged to simultaneously carry blanks from the shearing station 19 to a first die station 24, from the die station 24 to a second die station 26, from die station 26 to a third die station 27 and from the die station 27 to an extrusion die station 28. The transfer scissors 23 are mounted on a carriage 29 which reciprocates horizontally back and forth in front of the die breast to accomplish this action. The transfer scissors 23 are operated to grip blanks ejected from the dies and progressively position the blanks in front of the next station for the subsequent operation. The entire transfer system is powered by the countershaft 14 in timed relationship to the movement of the slide 17 so that blanks are progressively moved to each of the die stations. The structure illustrated for transferring the blanks progressively to each of the blank working stations is disclosed in detail in the United States patent to Clouse No. 2,026,823, dated January 7, 1936.

Referring to FIGURE 1, the wire stock 18 is fed through the die breast at the shearing station 19 until it engages in adjustable stock gauge 31 mounted on the frame 10. When the stock 18 engages the gauge 31, the proper amount of stock necessary to form the finished article extends beyond the face of the hardened bushing mounted in the frame which cooperates with the knife 22 to shear the blank 21. It is important that the blank 21 be accurately sized so that the proper amount of material will be provided to completely form the finished article without over-filling the dies which could cause excessive pressure and in extreme cases, die breakage.

The transfer scissors 23 operate to carry the blank 21 to the first die station 24 while the slide 17 is in its retracted position. To eject the blanks into the scissors 23 a rocker shaft 25 is mounted on the frame 10 and is oscillated by a connecting rod 25a journaled on an eccentric at the end of the crankshaft 11. An adjustable rocker arm 25b is provided for each die station which is operated by the rocker shaft 25 to power the ejector.

Referring to FIGURE 3, the first die station includes a die sleeve 32 mounted in the die breast 16 and formed with a central bore 33. A knockout tool 34 extends along the bore 33 and is formed with an end face 36 closing the bore 33 and cooperating with the walls thereof to define a die cavity. The rearward end of the die sleeve 32 is formed with a second bore 37 coaxial with and having a diameter substantially larger than the first bore 33. The bores 33 and 37 are joined by a conical shoulder 38. Positioned behind the die sleeve 32 is a backup plate 39 engaging the rearward end of the die sleeve on its forward side and seated against the frame 10 on its rearward side. The backup plate 39 is formed with a central bore 41 coaxial with and having a diameter substantially smaller than the bore 37. The knockout pin 34 slides in the bore 33. A filler 42 slides in the bore 37 and extends between the pin 34 and the backup plate 39 when the knockout pin is in its rearwardrnost position to limit such rearward movement and transmit the upsetting thrust from the knockout pin 34. The enlarged shoulder 42 is provided with a forward conical face 44 engageable with the conical shoulder 38 to limit forward movement of the filler 42. The rearward end of the filler 42 is provided with a stem 46 projecting through the bore 41 and engaged by a knockout pin 47 slidably mounted in the frame 10. At the completion of the working stroke, at the first work die station 24, the knockout pin 34 is pushed forward by the pin 47 and associated rocker arm 25b to eject the blank from the die sleeve 32 into the transfer scissors 23 which transport the blank to the second die station 26.

Mounted on the slide 17 at the first die station 24 is an upseting tool 48, the forward end of which projects into the bore 33 when the slide 17 moves to its forwardmost position. The tool 48 is anchored in the slide 17 by a mounting sleeve 49 against a backup plate 51. Both the end face 36 of the knockout pin 34 and the forward end of the upsetting tool 48 are formed with shallow recesses 52 and 53, respectively. The ends of the blank are, therefore, laterally supported in the recesses 52 and 53 during the upsetting operation. Both the knockout tool 34 and the upsetting tool 48 are formed with forward extending conical surfaces 54 joining the surface of the recesses 52 and 53 with an annular radially extending face 56.

As the upsetting tool 48 is carried forward by the slide 17, it engages the initial blank 21 and pushes it into the bore 33 until its inner end engages the recess 36. Continued movement then produces upsetting causing the blank to radially expand to form the first intermediate blank 57, illustrated in FIGURE 10. The first intermediate blank 57 has a central section which is thicker than the peripheral portion. As the slide moves back after the upsetting stroke, the knockout pin 47 pushes the knockout tool 34 forward, ejecting the blank 57 into the transfer scissors which transport the first intermediate blank to the second die station 26. The grain pattern of the intermediate blank 57 is symmetrical about the axis with relatively even radial flow lines except in the zone of the axis.

Located at the second die station 26 is a die sleeve 58 mounted in the die breast 16 and positioned at its rearward end against a backup plate 59 engaging the bed frame 10. The die sleeve 58 is formed with a central bore 61 having the diameter substantially equal to the diameter of the first intermediate blank 57. Behind the bore 61 the die sleeve is formed with a second bore 62 having a diameter slightly larger than the bore 61 and a third bore 63 having a diameter larger than the bore 62. A stripper sleeve 64 is formed with a forward end slidably fitting in the bore 61 and a rearward flange 66 sliding in the bore 62. The flange 66 is engageable with a shoulder 67 between the bores 61 and 62 to limit the forward movement of the stripper sleeve 64. The rearward movement of the stripper sleeve 64 is limited by engagement of its rearward face 65 with a forward side of a mounting plate 68 positioned in the bore 63 and held in engagement with a shoulder 69 joining the bores 62 and 63. A second mounting plate 71 is positioned in the bore 63 and is pressed between the backup plate 59 and the mounting plate 68.

A socketing tool 72 projects through a bore 73 in the stripper sleeve 64 and is seated at its rearward end against the second mounting plate 71. A shoulder 75 cooperates with a mating bore 74 and shoulder 76 in the first mounting plate 68 to securely anchor the socketing tool 72 in the position illustrated. A plurality of knockout pins 78 symmetrically located around the central axis of the tooling extend through the mounting plates 68 and 71 and engage the rearward end of the stripper sleeve 64. Rearward of the knockout pin 78 is a knockout rod 79 and a spacer pin 79a slidably mounted in the bed frame 10 and backup plate 59 respectively. The knockout rod 79 is pushed forward by its associated rocker arm 25b through the spacer pin 79a and knockout pins 78 moves the stripper sleeve 64 forward to eject the blank from the second die station 26. When the stripper sleeve 64 is in its rearward position, its forward end is rearwardly spaced from the forward end of the socketing tool 72.

Mounted on the slide 17 at the second die station 26 is a tool 80 positioned at its rearward end against a backup plate 81 and laterally supported in a mounting sleeve 82. The forward end of the tool 80 is proportioned to fit into the bore 61.

As the slide 17 moves forward, the first intermediate blank 57 positioned at the second die station is engaged by the tool 80 and pushed into the die sleeve 58 until its inner end engages the socketing tool 72. Continued movement causes the blank to be socketed forming a second intermediate blank 83 having a central bore 84 extending a substantial distance therethrough. The metal displaced by the socketing to form the bore 84 is radially displaced by this operation.

As the slide 17 moves back after the completion of the working stroke, the operator 79 is moved forward by its arm b causing the stripper sleeve 64 to push the blank forward out of the die into the transfer scissors which transport the second intermediate blank to the third die station 27.

Referring to FIGURE 5, the dies of the third die station 27 include a die sleeve 86 having a bore 87 with a diameter substantially equal to the diameter of the second intermediate blank 83. The die sleeve 86 is mounted in the die breast 16 against a backup plate 88. The elements and operation of the dies in the third die station are similar to those in the second station 26 in that a stripper sleeve 89 extends into the bore 87 and is axially movable between the rearward position illustrated and a forward position to which it is moved to eject the blank from the die sleeve 86. A punch 91 is mounted in mounting plates 92 and 93 and extends forward of the stripper sleeve 89. The stripper sleeve 89 is engaged at its rear ward end by knockout pins 94 which are operated by a knockout opera-tor 96.

The forward end of the stripper sleeve 89 is spaced back from the forward end of the punch 91 by a distance greater than the thickness of the intermediate blank. A hollow tool 97 is seated against a backup plate 98 and secured to the slide 17 by a mounting ring 99. The forward end of the hollow tool 97 is formed with a bore 101 substantially equal in diameter to the diameter of the punch 91 which cooperates therewith to shear away the web of material at the end of the bore 84 in the second intermediate blank forming a slug 102 which is the only scrap resulting from the manufacture. The slug 102 is thin since the bore 84 of the second intermediate blank extends a substantial distance through the blank. Rearward of the bore 101, the hollow tool 97 is formed with a larger diameter passage 103 along which the slugs 102 move to a lateral opening 104 through which the slugs drop to the bottom of the machine where they are removed. Since the bore 101 tightly fits the slug 102 it will not fall out the forward end of the tool when the slide is retracted. The forward end 106 of the tool 97 is flat so that it engages the outer side of the second inter-mediate blank 83 adjacent to the area to be punched.

As the slide 17 moves forward, the second intermediate blank positioned in front of the third die station by the transfer scissors is engaged by the end of the hollow tool 97 and pushed into the bore 87 of the die sleeve 86. The blank is moved along the bore 87 until it contacts the punch 91. Continued movement of the blank under the influence of the tool 97 causes the blank to be punched forming a through-bore therein and resulting in a third intermediate blank 107. The material of the slug 102 removed from the blank is the only material which has not been radially displaced. Therefore all of the material of the blank 107 is substantially uniformly worked. By forming the third intermediate blank 107 according to the process as described above, the blank has substantially uniform cold working throughout and the grain structure is substantially symmetrical around the central axis of the blank. This symmetrical grain structure and uniform cold working results in superior extrusion eliminating flaws in the final product and preventing the occurrence of excessive pressures due to hard spots in the blank.

As the slide 17 carries the tool 97 back from the die breast 16 the operator 96 is moved by its rocker arm 25b to push the stripper sleeve 89 forward ejecting the third intermediate blank 107 from the dies into the transfer scissors which transfer the blank to the extrusion station 28 wherein the final article is formed.

Mounted at the extrusion die station 28 is an extrusion die element 108 positioned at its rearward end against a die sleeve 109. Both of the dies 108 and 109 are mounted in a die holder 111 which is in turn mounted in the die breast 16. The outer surface of the extrusion die 108 is formed as a cone engaging a mating cone 112 in the die holder 111. A mounting ring 113 is threaded into the rearward end of the die holder 111 pressing the die sleeve 109 and in turn the extrusion ring 108 forward locking the dies in the holder. A knockout pin 114 is slidably mounted in the bed frame 10 and projects at its forward end into a bore 116 formed in the die sleeve 109. The bore 116 extends to a radial shoulder 117 which extends from the bore 116 to a second bore 118. The bore 118 in turn opens to a conical surface 119 extending to the forward face of the die sleeve 109 where it engages the extrusion die 108. The extrusion die 108 is formed with an extrusion bore 121 having a diameter substantially equal to the diameter of the third intermediate blank 107.

Mounted on the slide 17 is a tool 122 having a rearward flange 123 locked against the slide 17 by a mounting ring 124. The tool 122 is formed with a rearward cylindrical portion 126 closely fitting and laterally supported by the mounting ring 124 which extends to a radius portion 127 tangentially blending into the extrusion portion 128. The radius of the extrusion portion 128 is less than the radius of the extrusion bore 121 by the thickness of the wall of the finished piece.

The forward end of the tool 122 is formed with a conical face 129 extending from the extrusion portion 128 to a tapered nose 131 having a diameter at its forward end fitting with clearance the bore in the third intermediate blank 107. The end of the knock-out pin 114 is formed with a blind bore to receive the nose of the tool 122 at the end of the stroke.

As the slide 17 moves forward, the third intermediate blank position at the extrusion die station 28 is pushed into the die 108 by the tool 122. The nose 131 enters the bore 110 and when the elements reach the position illustrated in FIGURE 7, the intermediate blank 107 engages the conical surface 119 at its intersection with the bore 121 and the forward surface of the blank is engaged adjacent to its bore 110 at the intersection between the conical portion 129 and the nose 131. The action which first occurs is dishing of the blank and then forward extrusion to the position of FIGURE 8. Forward movement of the extrusion tool 122 causes the material of the blank to be forward extruded with the nose 131 along the bore 118 to the shoulder 117. The shoulder 117 provides a substantial increase in resistance to forward extrusion though a small amount of the blank does extend beyond the shoulder between the nose 131 and the bore 116 until it engages the end of the knock-out pin 114 preventing further forward extrusion.

The material of the blank then extrudes back along the bore 121 and the extrusion portion 128 until the cornpleted article is formed as shown in FIGURE 6. A stripper ring 133 is mounted to surround the portion 128 and is fixed against movement relative to the die breast. Therefore, as the tool 122 is carried back from the dies, the stripper 133 engages the end preventing rearward movement of the extruded tube with the tool. Normally, the friction of the tubular article on the tool carries the article back clear of the dies, however, the knock-out pin 114 is pushed forward by its rocker arm 25b to in- 7 sure ejection of the finished blank from the dies 108 and 109.

The knock-out pin 114 limits the forward extrusion to a predetermined amount and insures that a sufficient amount of blank material will be backward extruded to form the tubular portion of the required length. Since the grain of the third intermediate blank 107 is symmetrical about the central axis and since the extrusion is also symmetrical about the central axis of the finished article, a uniform degree of extrusion will occur during the formation of the final article.

It should be understood that even though the method and apparatus incorporating this invention is illustrated in conjunction with extrusion of a collapsible tube of the type generally used to dispense toothpaste, paint pigments and the like, the invention can be used to form other articles such as aerosol cans of cup-shaped articles. This invention finds particular application in the extrusion of metals such as aluminum, lead and other similar relatively soft metals used to form collapsible tubes. However, cold Working produces increased strength, particularly in aluminum which is important for non-collapsing containers such as those used in aerosol cans and the like.

Although a preferred embodiment of this invention is illustrated, it is to be understood by those skilled in the art, that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention as defined in the following claims.

What is claimed is:

1. A method of forming hollow articles from a material subject to grain growth aging comprising sequential steps of symmetrically upsetting a cylindrical piece of stock increasing its radius and decreasing its length, thereafter socketing said stock a substantial distance therethrough forming a blind passage along the central axis thereof, thereafter punching a slug from said stock forming a central passage through said stock thereby leaving only material which has been radially displaced, and thereafter symmetrically extruding a hollow article, the period of time between each step being sufficiently short to prevent substantial aging of said material.

2. A method of forming hollow articles comprising upsetting cylindrical blanks within a confined die exerting an axial force on the ends of the blank causing substantially symmetrical radial flow of the material thereof thereby forming an intermediate cylindrical blank, thereafter pressing a socketing tool a substantial distance through said blank forming a blind passage along the axis thereof, thereafter shearing a slug from the intermediate blank thereby extending said passage completely through said intermediate blank, and thereafter extruding said intermediate blank symmetrically about the central axis thereof to form a hollow article.

3. A method of forming hollow articles comprising the steps of upsetting cylindrical blanks within a confined die exert-ing an axial force on the ends of the blanks causing substantially symmetrical radial flow of the material thereof thereby forming an intermediate cylindrical blank, thereafter pressing a socketing tool a substantial distance through said blank forming a blind passage along the axis thereof, thereafter shearing a slug from the intermediate blank thereby extending said passage completely through said intermediate blank, and thereafter extruding said intermediate blank symmetrically about the central axis thereof to form a hollow article, the period of time between each step being uniform.

4. A method of forming tubular articles comprising upsetting a cylindrical piece of stock increasing its radius and decreasing its length thereby producing a blank head having symmetrical radially extending flow lines, forming a central passage through said blank leaving only stock having substantially uniform degrees of working, and thereafter forward extruding a portion of said stock adjacent to said passage forming a tubular boss and backward extruding a substantial portion of the remaining stock forming a tubular wall having a diameter substantially equal to the diameter of said blank and substantially greater than the diameter of said boss, said extrusion resulting in a thin-end wall joining said tubular Wall and boss.

References Cited by the Examiner UNITED STATES PATENTS 1,261,084 4/1918 Wilcox 78-17 1,468,092 9/ 1923 Towne 207-10 1,480,843 1/ 1924 Singer 72-368 2,227,440 1/ 1941 Church 207- 2,270,988 1/ 1942 Woods 72-368 2,687,660 8/1954 Friedman 78-17 2,911,861 11/1959 Nilgen 78-17 3,054,177 9/ 1962 Duhamel 29-534 3,078,566 2/1963 Egan 29-534 FOREIGN PATENTS 716,130 9/1954 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

G. P. CROSBY, Assistant Examiner. 

1. A METHOD OF FORMING HOLLOW ARTICLES FROM A MATERIAL SUBJECT TO GRAIN GROWTH AGING COMPRISING SEQUENTIAL STEPS OF SYMMETRICALLY UPSETTING A CYLINDRICAL PIECE OF STOCK INCREASING ITS RADIUS AND DECREASING ITS LENGTH, THEREAFTER SOCKETING SAID STOCK A SUBSTANTIAL DISTANCE THERETHROUGH FORMING A BLIND PASSAGE ALONG THE CENTRAL AXIS THEREOF, THEREAFTER PUNCHING A SLUG FROM SAID STOCK FORMING A CENTRAL PASSAGE THROUGH SAID STOCK THEREBY LEAVING ONLY MATERIAL WHICH HAS BEEN RADIALLY DISPLACED, AND THEREAFTER SYMMETRICALLY EXTRUDING A HOLLOW ARTICLE, THE PERIOD OF TIME BETWEEN EACH STEP BEING SUFFICIENTLY SHORT TO PREVENT SUBSTANTIAL AGING OF SAID MATERIAL. 